The invention relates generally to devices for digitizing the coordinates of a three dimensional object. More particularly, it is directed to such a three dimensional digitizer that employs an electromagnetic coupling.
Apparatus for digitizing the coordinates of a two dimensional drawing with an electromagnetic coupling are known in the prior art. Such prior art drafting and digitizing apparatus comprises an automatically controlled carriage that is translated over a drawing support surface of a digitizing and plotting table. A cursor is disposed on the carriage for tracing a drawing disposed on the support surface, the cursor having a pair of electromagnetic coils which are used to produce signals indicative of the relative position of the carriage and cursor during the digitizing mode of operation. However, such devices are capable of monitoring a cursor having only two degrees of freedom. Since the orientation of the cursor relative to the work surface must remain fixed, these devices are incapable of digitizing the coordinates of a three dimensional model. While other devices are found for accomplishing three dimensional digitizing, these devices employ optical couplings, acoustic couplings, manual measurements, or measurements using potentiometers and the like for determining the coordinates of the three dimensional model. Prior art three dimensional digitizers do not feature electromagnetic couplings between the tracing device and a processor.
The art of tracking objects with electromagnetic radiation is highly developed. Such systems have been used, for example, for guiding an aircraft to a landing site, guiding an excavating device, tracking targets and aiming military ordinance. In the latter case, the source of electromagnetic radiation is fixed with respect to the frame of an aircraft and the receiver is mounted in the pilot's helmet in a calibrated relationship with respect to a helmet mounted reticle. The analyzing means associated with the receiver repetitively calculates the position and orientation of the pilot's head with respect to the air frame, and the pilot visually designates and/or tracks a target with the helmet mounted reticle to initially aim the computer guided ordinance which is released from the aircraft.